Salivary mucins are high molecular weight glycoproteins which have multiple protective functions in the oral cavity. Two distinct mucin family members are present in human saliva: The lower molecular weight species MG2, and the high molecular weight, multi-subunit component MG1. Both mucins are composed of several structural domains, each of which may be responsible for discrete biological functions. However, the distribution of the structural domains, their spacial orientation about the mucin molecule, and the in-situ distribution of these domains within salivary gland tissue, have yet to be adequately determined. The purpose of this project is to apply recent advances in monoclonal antibody technology for the detailed immunochemical and immunocytochemical characterization of salivary mucin structural domains. We will establish a well-characterized library of monoclonal antibodies for use as specific probes of mucin structure. These defined reagents will then be used with immunoblotting, Western transfer analysis, and two-dimensional SDS-PAGE, to epitope map mucin molecules. Such studies will provide details of the relative arrangement and orientation of mucin structural domains, and will thus provide new information which will enhance our understanding of mucin's structure. Monoclonal antibodies will also be used to immunocytochemically survey mucin structural domains within the major and minor mucin-secreting salivary glands. The antigenic profile and intercellular distribution of these domains will be established for normal tissues using both direct and indirect enzyme techniques, as well as by single-and multi-labeling methods. These findings will then be compared with those found for neoplastic salivary gland tissues using pleomorphic adenoma, mucoepidermoid carcinoma, and adenocystic carcinoma as models. Such procedures may aid in the identification of the cells of origin of these tumors, and in the identification of mucin epitopes in poorly differentiated salivary gland neoplasms.